In transport systems in which transport cars run on profile rail lines and receive their drive energy from current paths proceeding along the profile rail lines, the transport cars often serve for the transport of the most various goods. For example, files, hardware for a mechanical fabrication, rolls of drawings, or laboratory samples stored in test tubes or similar glass vessels, are transported. In this connection, it is known to employ different transport containers which are specially adapted to specific goods. Thus, for example, large cylindrical containers are employed for transporting rolls of drawings, and containers with rotatable receptacles are employed for transporting test tubes so as to guarantee a vertical alignment of the test tubes in any position (angular attitude) of the transport car. It is further known to construct the transport car so that the basic self-propelled chassis or carriage including the drive motor, control devices and the transport rollers, detachably mounts a separate transport container, whereby the basic transport chassis or carriage can be coupled by means of a correspondingly adapted locking device with any of a number of different transport containers to form a transport car unit.
This method of building up a transport car from a basic transport carriage and a transport container which can be released therefrom implies a number of monitoring problems. Thus, for example, it is usually demanded that the basic transport carriage be able to travel along the profile rail lines without a transport container placed onto it. This possibility is useful, for example, since it enables the delivery of the transport carriage to a dispatching station where special containers are always present in response to a request issued by such dispatching station. On the other hand, the travel of the transport carriage with transport containers only loosely in place but not locked is to be prevented for reasons of safety. Beyond that, as in transport cars in which the actual transport container and the transport carriage form a structural unit, it must be insured that a departure of the transport car is impossible when the cover of the transport container is not closed. For such monitoring tasks, among other things, a contact device is employed on the transport chassis or carriage which may be influenced by means of a transport container resting on the transport carriage. Thereby, for example, the contact device can be inserted in a drive current circuit of the transport chassis or carriage in such manner that the driving current circuit is closed without a transport container put in place, but, on the other hand, is interrupted when a transport container is loosely or firmly put in place. A second driving current circuit can be connected in parallel to this current circuit, which second current circuit includes a cover locking contact and a locking contact proceeding over the locking device for the transport carriage and transport container and which, accordingly, only allows a driving current circuit for the transport car when both the transport container is firmly placed and locked onto the transport carriage, and the cover of the transport container is closed.